Generally, various types of electrical components and signals generated therefrom can be adversely affected by exposure to various radio signals and electrical fields that produce electro-magnetic radiation (EMR). Undesirable EMR is considered Electro-Magnetic Interference (EMI), aka Radio Frequency Interference (RFI)). EMI can damage electrical components and/or interfere with signals generated or received by the electrical components. In contrast, desirable EMR is used to establish electrical and/or magnetic signals.
As an electronic device often contains both desirable and undesirable sources of EMR, in order to protect some electronic components from EMI and/or enclose other electronic components to prevent attenuation of desired EMR, a Faraday cage can be utilized. A Faraday cage, often referred to as a Radio Frequency (RF) shield, can be used to enclose a specific electronic component to minimize the effects of EMI on electrical components enclosed therein. When an RF shield is exposed to an exterior source of EMI, the RF shield isolates the electric wave portion of the EMI about the exterior of the cage, while the cage attenuates the magnetic wave portion that passes through the cage, thereby reducing the strength of the EMI field experienced by the electronic component. Likewise, an RF shield can be used to maintain the field strength of a desirable EMR that is being emitted from within the RF shield.
An RF shield typically includes a shield fence secured to a Printed Wiring Board (PWB) (aka Printed Circuit Board). The shield fence is covered (i.e., capped) by an outer shield cover, thereby forming an enclosed and protected area. Various methods of securing the shield cover to the shield fence have been used. In large part, these methods have included numerous drawbacks and limitations. For example, the shield cover can be soldered to the shield fence, except when a volatile gas or heat sensitive components are being enclosed, due to the heat generated during the soldering process. Further, the failure rate of soldering can be significant, and in the event of failure, solder cannot be removed and re-applied because of delamination. Other methods have included providing a shield cover with extended walls, along with a wide gutter along the bottom of the shield fence, at the circuit board juncture, for receiving therein the edges of the shield cover walls. This method requires a large gutter thickness for an interference fit with the shield cover. Due to standard manufacturing tolerance limitations, gaps would inherently exist at one or more points along the interconnection.
Yet another method utilizes a plurality of slots in the shield cover which align with a plurality of twist-lock protrusions from the walls of the shield fence. This method requires precision placement of the shield cover to align with each of the slots, along with the need for rotating each of the protrusions to fasten the shield cover to the shield fence. In addition, the inherent tendency of metal to fracture upon twisting can result in one or more of the protrusions being broken off during assembly. Further, the aforementioned methods often require the RF fence to have taller walls to accommodate the installation methods, and therefore the RF shield will have an unnecessarily larger volume, thereby increasing undesirable moding and reducing performance of shielded components.
As can be ascertained from the above discussion, the aforementioned methods are often expensive and complicated to implement during manufacturing and are often found wanting in terms of performance and reliability. Accordingly, it is desired that a device and method be provided that overcomes one or more of the aforementioned drawbacks and/or one or more other drawbacks.